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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script type="text/javascript" src="./min.js"></script>
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<body>
    
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<script type="text/javascript">var r=prompt("输入圆的半径","请输入半径：");//prompt() 方法用于显示可提示用户进行输入的对话框
    if(r!=null)
    {
        var square=r*r*Math.PI;
        document.write("圆的面积为："+square);
    }
    else
    {
        alert("输入数据有误");
    }
 
 
 
 
 </script>

</html>